I had very severe depression when I was 18. I've had a few severe episodes of depression, but that episode was the worst in terms of being so severe I developed psychosis with fairly serious paranoia (I thought people were trying to poison me, were spying on me, could read my thoughts, etc...) I'm now healthy mentally and don't really get paranoid much at all (probably less than most people do because I've been there and I know how the thought patterns work.)
Anyway, I just want to say that even if you have a tendency to mental health problems, psychosis is a temporary state even if it comes back at some point in your life. The worst part of it for me was being in my own world and not feeling like I could escape the thoughts in my head. Go and get some help and be honest about exactly how it is for you and you will be able to recover much more quickly. I know this is a VERY difficult thing to do when you're paranoid, but it's what I wish I did in hindsight. If you know that your thoughts are not rational then that shows that you aren't 'insane', you're just struggling with mental health. Bear this in mind and feel proud of how much you ARE coping already, then you will feel more empowered to get better.
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Zombies, zombies will tear us apart...again.